Enhance NavigationMixin to handle notifications

pkg/analyzer_plugin/lib/plugin/navigation_mixin.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer_plugin/plugin/plugin.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart';
@@ skipping 11 matching lines @@
  * Clients may not extend or implement this class, but are allowed to use it as
  * a mix-in when creating a subclass of [ServerPlugin] that also uses
  * [NavigationMixin] as a mix-in.
  */
 abstract class DartNavigationMixin implements NavigationMixin {
   @override
   Future<NavigationRequest> getNavigationRequest(
       AnalysisGetNavigationParams parameters) async {
     String path = parameters.file;
     ResolveResult result = await getResolveResult(path);
+    int offset = parameters.offset;
+    int length = parameters.length;
+    if (offset < 0 && length < 0) {
+      offset = 0;
+      length = result.content.length;
+    }
     return new DartNavigationRequestImpl(
-        resourceProvider, parameters.offset, parameters.length, result);
+        resourceProvider, offset, length, result);
   }
 }
 
 /**
  * A mixin that can be used when creating a subclass of [ServerPlugin] to
  * provide most of the implementation for handling navigation requests.
  *
  * Clients may not extend or implement this class, but are allowed to use it as
  * a mix-in when creating a subclass of [ServerPlugin].
  */
@@ skipping 18 matching lines @@
       AnalysisGetNavigationParams parameters) async {
     String path = parameters.file;
     NavigationRequest request = await getNavigationRequest(parameters);
     NavigationGenerator generator =
         new NavigationGenerator(getNavigationContributors(path));
     GeneratorResult result =
         await generator.generateNavigationResponse(request);
     result.sendNotifications(channel);
     return result.result;
   }
+
+  /**
+   * Send a navigation notification for the file with the given [path] to the
+   * server.
+   */
+  @override
+  Future<Null> sendNavigationNotification(String path) async {
+    try {
+      NavigationRequest request = await getNavigationRequest(
+          new AnalysisGetNavigationParams(path, -1, -1));
+      NavigationGenerator generator =
+          new NavigationGenerator(getNavigationContributors(path));
+      GeneratorResult generatorResult =
+          await generator.generateNavigationNotification(request);
+      generatorResult.sendNotifications(channel);
+    } on RequestFailure {
+      // If we couldn't analyze the file, then don't send a notification.
+    }
+  }
 }